1. Field of the Invention
The invention relates to a configuration for supplying ink to an ink jet print head, in particular an ink jet print head composed of a plurality of stacked modules.
Such ink jet print heads are used both in office printers and in small high-speed printers--of the kind needed for postage meters and product labeling devices--and as a rule have a relatively large number of jets.
Precisely in this latter application, high reliability is demanded, so that mistakes in printing that can have major cost consequences are averted. One component that has an especially great influence on the reliability of a printer is the ink jet print head, along with its supply.
It is a well known principle that the reliability of components increases as the number of individual parts decreases. This is where the invention sets in.
2. Description of the Related Art
It has been known--see German patent disclosures DE 44 43 244 A1 and DE 44 43 245 A1, and U.S. Pat. No. 4,703,333--to connect at least one ribbon conductor to each module of an ink jet print head composed of a plurality of ink jet printing modules. The printing operation is thereby controlled from a central point and the current is supplied via a ribbon conductor.
In U.S. Pat. No. 4,703,333, each module has a number of jets and comprises a plurality of stacked plates with ink jet printing chambers and ink supply conduits machined into them. The module is a so-called sideshooter. This means that the nozzle conduits or openings are guided crosswise through an outer plate. The pressure wave in the ink jet printing chamber extends in the direction of the jet conduit, so that the ink droplets are expelled orthogonally to the plate. Correspondingly, ink inlet conduits and openings for the ink supply are provided crosswise through the outer plate on the opposite side of the module. To that end, an inlet connecting stub is mounted onto the plate above each ink inlet opening. The inlet connecting stubs, located in a row, of all the modules communicate with an ink tank via a common adapter with a following ink hose. The adapter is embodied as a fluid distributor element. Connecting stubs, which are slipped into the inlet connecting stubs of the modules, are located on its ink outlet side. On its ink inlet side is a connecting stub onto which the ink hose is slipped.
The problem of equalizing pressure for the ink inlet remains unaddressed in that disclosure.
For this ink jet print head, a scale-like configuration of the modules is necessary. On the one hand, an unhindered expulsion of ink via a side wall should be possible--because it is the sideshooter type--and on the other, enough space should be available for the ink inlet. Overall, this means that a correspondingly large amount of space is needed.
A multicolor ink jet printer with a movable ink jet print head is also known--see German patent disclosure DE 33 35 614 A1--in which on the one hand fixed ink lines lead from the various ink tanks to the ink jet print head, and on the other, flexible hoses lead from the air spaces above the ink chambers in the ink tanks to the outer wall of the printer; outside the ink tank, the hoses are joined together on the order of a ribbon cable.
Because of the rigid connection between the ink tanks and the ink jet print head, all the ink tanks must be moved in common together with the ink jet print head. This is problematic, given such a relatively large mass.
Ink jet print heads comprising individual modules in a stacked construction that operate by the edgeshooter principle is known as well in the prior art. See German patent DE 44 43 254 C1. The single module comprises three plates one above the other. When the modules are joined into an ink jet print head, spacer parts are also inserted between adjacent modules. Nothing further is tought about how the ink is supplied.
A configuration for an ink jet print head of the piezoelectric planar type is also known--see German Utility Model DE 295 21 128 U1, in which plates are also layered one above the other, and ink supply conduits, ink jet printing chambers, nozzle conduits and nozzle openings are machined into them. The ink supply conduits are supplied from a common supply conduit.
Finally, an ink jet printer is known from Japanese patent disclosure JP 5-116277 A1, in which a separate ink ribbon conductor and a separate electrical ribbon conductor are secured, one above the other, by means of a snap clip to a carriage that additionally carries the ink jet print head. The electric ribbon conductor serves the purpose of electrical supply and triggering of the ink jet print head. The ink ribbon conductor serves to supply the ink jet print head with fresh ink via an intermediate reservoir and to dispose of old ink.